In many modern technical installations, process control systems are used to make operation of the respective installation as safe as possible and to alternate as many functions of the technical installation as possible.
If, in past times, a large number of people were still entrusted with the operation of a technical installation, then today the same spectrum of task is covered by a much smaller number of people, assisted by a process control system which informs the operating personnel of the operating state and receives and automatically executes commands which are to be executed, one command being able to comprise a number of subcommands.
In the course of time, so many tasks originally aimed at humans have been transferred to the process control system that the number of operators required to operate a technical installation has decreased steadily over time.
Process control systems used previously were normally in the form of computer systems which have been developed specifically for process control and which executed software developed on an individual basis for the respective instance of use, which meant that the operation of such a system was reserved for specialists who not only had to be exactly familiar with the operation of the technical installation to be controlled but also had to undergo comprehensive training in the operation of such a special process control system.
In the course of time, although process control systems appeared which were developed by various manufacturers and where respectively standardized on a manufacturer-specific basis, which meant that operating personnel for one technical installation could also be employed for another technical installation controlled using a similar process control system, the operation of such process control systems also required the use of a normally specific hardware environment and of a specifically developed software environment. Such process control systems normally cannot be operated by computers of almost any design, but require the use of specifically designed computers. In addition, the use of process control systems in technical installations up until now often require the use of a specific operating system, for example UNIX or specific further developments bases thereon, since the other operating systems widely used and known, for example the Windows operating system, used predominantly in the office environment, do not have the characteristics required for a process control system, such as speed and/or reliability and/or real-time capability.
Up until now, a user of a known process control system has therefore had to apply knowledge about the use of operating systems which are not so widely used. The user has not simply been able to fall back on knowledge which he has already possessed about widely used operating systems.
In addition, with known process control systems, it has been difficult to couple them to other computer systems, for example in order to control functions of the process control system using another computer system which has been coupled. This coupling has normally required multistage conversion of the various data formats among one another, which also required account to be taken of the usually different transmission protocols for the transmission media used. Furthermore, such couplings have needed to be planned and implemented separately for each individual instance of application in practice. Every such coupling has been an individual solution in practice.
A particular difficulty has been coupling systems described previously, particularly if these systems have run under different operating systems and/or have used data transmission media having different characteristics and/or if various transmission protocols have needed to be matched to one another.
The company brochure web4txp, Siemens AG, published in 2000, describes a process control system which can be connected to the Internet and can be operated using the Internet.
A process control system of such design allows the operating personnel to control a technical installation using a personal computer (PC) which runs under a widely used operating system, for example Microsoft Windows, and which additionally needs to hold just an “Internet browser”, in principle. Internet browsers are very widely used and are accordingly known to a large number of people, not just from relevant technical circles.
To be able to operate a technical installation, an operator therefore no longer has to acquire extensive special knowledge about the operation of a specific process control system, but rather can operate the technical installation by falling back on knowledge which he normally already has, for example the operation of a (standard) Internet browser whose functionality is already known to a very large number of people today.
Such a process control system contains a separate Internet server which connects the process control system, including automation systems, control computers and engineering computers, to an intranet and/or to the Internet.
A drawback of a process control system of such design is that, although the Internet server allows interplay between the two worlds—for example Windows PCs in an intranet, on the one hand, and a UNIX-based process control system, on the other—, the two cited systems continue to be self-contained, which means that, if the Internet server fails, for example, the computers in the process control system are not able to perform any functions, for example Internet access, which are beyond the functions intended and planned for the process control system. In addition, in the event of the Internet server failing, it is not possible, by way of example, to use a PC connected to the intranet to access the process control system, even though said process control system may be fully functional. Moreover, the use of a separate Internet server means an additional source of error which can result in the loss of the technical installation's control and observation functions using a PC connected to the intranet.
In addition, such a control system does not preclude the control system buses (terminal bus, plant bus) having data applied to them which are not connected to the actual control and observation of the technical installation which is to be controlled, which means that the control system buses described can be blocked by such “foreign data” and therefore their normal functionality can be restricted or even—at least temporarily—lost.